Conventionally, in a rotating electric machine driver, the electric current in each of three phases is detected based on a detected electric current value of a shunt resistor that is disposed on a bus line of an inverter. For example, in a patent document 1 (i.e., Japanese Patent Publication: JP-A-2013-110864), two systems of circuits, which respectively amplify the voltage between both ends of the shunt resistor, are provided.
In the patent document 1, it is disclosed that faults and abnormalities of the current detector circuit are detected by having the two systems of circuits for amplifying the voltage between both ends of the shunt resistor.
However, the technique in the patent document 1 cannot detect the abnormalities (hereinafter “open failure”) and other faults which disable a connection of the switching element in the inverter, that is, disables a switch ON of the switching element. The open failure disabling the conduction of the switching element may not only arise from an abnormality of the switching element itself but may also arise from an abnormality of an instruction signal that switches ON the switching element.